In situ tracking the reversible spinel-rocksalt structural transformation between Mn3O4 and MnO.

Electron beam irradiation is well known to induce damage in materials. The structural transformation involved in the damage is usually believed to be an irreversible solid state chemical reaction. Here we use in situ transmission electron microscopy (TEM) combined electron-energy loss spectroscopy (EELS) technique in an aberration-corrected TEM to track the structural transformation in spinel Mn3O4 induced by electron beam irradiation. It is clarified that spinel Mn3O4 is transformed to rocksalt structured MnO by irradiation and the reversed recovering transition from rocksalt MnO to spinel Mn3O4 can occur by aging in the gentle electron beam circumstance. The mechanisms including the role of O desorption/adsorption and the displacement of Mn and O involved in the reversible transformation processes are discussed. The work presents an implication that electron beam can modify the structure at atomic dimension yielding diverse assemblies of surfaces, interfaces and colorful properties.